Bhutan is one of my favorite places on earth. As a Buddhist, I find the people of Bhutan (Like Navajo people) to be very spiritual and compassionate.
Bhutan lies in the ridge of the mountains, so on the flight to Paro and I recommend a cessna to VQPR.
From there take off in a small craft with an open glass cockpit to fly around Bhutan to see the monasteries, Hydro dam, and more.
When flying from Nepal (not a too long of a flight. You will enjoy the rollig nhills and climb into the mountain (hills have a elevation of 5000+ feet. Your Cruise needs to be at least 9,500 to 10,500 to be safer , even tho you can rise over the higher crest just before the narrow valley to the Bhutan airport. Any lower then 8,500 feet and you well be hitting mountains.
From Nepal if you feel daring, take a flight to Tibet (I will NOT use China or the actions of the CCP to reference it) and to Lhasa.
Flying to Tibet and Lhasa means you will be going up very high. A cessna should be able to do it. But only the main airport can handle a Airbus and its a tight fast landing and stop. Depending on your flight difficulty, be careful of up and down drafts along the ridges. You can use flaps to control rising over ridges.